Decreasing object-to-receptor distance in dental radiography primarily results in which effect on image sharpness?

• A. Less beam divergence → sharper image
• B. More beam divergence → sharper image
• C. No change in sharpness
• D. Increased exposure leads to sharper image

Answer: (A)

Sharpness in dental radiography is governed by geometry: the smaller the geometric unsharpness, the crisper the image. Reducing the distance between the object and the receptor lowers geometric unsharpness because the divergent rays from the focal spot have less distance to spread before reaching the receptor, making edges more defined. In practical terms, bringing the tooth closer to the film (smaller object-to-receptor distance) decreases blur and increases sharpness, and this effect is described by the idea that geometric blur is related to the focal spot size and the object-to-receptor distance. Increasing beam divergence would blur edges, and exposure level affects brightness, not edge sharpness.